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Modelling hydrological performance of a bauxite residue profile for deposition management of a storage facility

- Shaygan, Mandana, Usher, Brent, Baumgartl, Thomas

  • Authors: Shaygan, Mandana , Usher, Brent , Baumgartl, Thomas
  • Date: 2020
  • Type: Text , Journal article
  • Relation: Water (Switzerland) Vol. 12, no. 7 (2020), p.
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  • Description: Accurate scheduling of bauxite residue (red mud) deposition time is required in order to prevent the risk of storage facility failure. This study was conducted to precisely determine the hydraulic parameters of bauxite residue and investigate the capability of HYDRUS to accurately estimate the residue moisture profile and the timing for its deposition. The hydraulic properties of the bauxite residue profile were determined by solving an inverse problem. A one-dimensional hydrological model (HYDRUS-1D) was validated using a 300 mm long column filled with bauxite residue and exposed to a dynamic lower boundary condition. After numerical validation, the model was used to simulate the moisture profile of bauxite residue under the climatic conditions of an alumina refinery site in Queensland, Australia, as well as other scenarios (i.e., high (300 mm) and small (1.7 mm) rainfall events of the site). This study showed that the HYDRUS model can be used as a predictive tool to precisely estimate the moisture profile of the bauxite residue and that the timing for the re-deposition of the bauxite residue can be estimated by understanding the moisture profile and desired shear strength of the residue. This study revealed that the examined bauxite residue approaches field capacity (water potential-10 kPa) after three days from a low rainfall event (<1.7 mm) and after eight days from an intense rainfall event (300 mm) at the time of disposal. This suggests that the bauxite residue can be deposited every four days after low rainfall events (as low as 1.7 mm) and every nine days after high rainfall events (as high as 300 mm) at the time of deposition, if bauxite residue experiences an initial drying period following deposition. © 2020 by the authors.

The effect of soil physical amendments on reclamation of a saline-sodic soil : Simulation of salt leaching using HYDRUS-1D

- Shaygan, Mandana, Baumgartl, Thomas, Arnold, Sven, Reading, Lucy

  • Authors: Shaygan, Mandana , Baumgartl, Thomas , Arnold, Sven , Reading, Lucy
  • Date: 2018
  • Type: Text , Journal article
  • Relation: Soil Research Vol. 56, no. 8 (2018), p. 829-845
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  • Description: Poor soil physical conditions such as low hydraulic conductivity can limit salt depletion from surface soil. Altering the pore system by addition of organic and inorganic amendments may improve salt leaching as a reclamation strategy. Column studies were conducted to investigate salt leaching in amended and non-amended soil profiles. A one-dimensional water and solute transport model (HYDRUS-1D) was also assessed for its applicability to simulate salt leaching for amendment strategy. Columns of length 300 mm were filled with saline-sodic soil at the lower end (100-300 mm) and then covered with soil amended with 40% (wt/wt) fine sand and 20% (wt/wt) wood chips, separately. A control column was filled with saline-sodic soil only. One rainfall scenario typical for a location in south-west Queensland (Australia) was applied to the columns. Water potentials were monitored using tensiometers installed at three depths: 35, 120 and 250 mm. The concentrations of individual cations (Na

Mapping the cumulative impacts of long-term mining disturbance and progressive rehabilitation on ecosystem services

- Wang, Zhenyu, Lechner, Alex, Yang, Yongjun, Baumgartl, Thomas, Wu, Jiansheng

  • Authors: Wang, Zhenyu , Lechner, Alex , Yang, Yongjun , Baumgartl, Thomas , Wu, Jiansheng
  • Date: 2020
  • Type: Text , Journal article
  • Relation: Science of the Total Environment Vol. 717, no. (2020), p.
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  • Description: Open-cut coal mining can seriously disturb and reshape natural landscapes which results in a range of impacts on local ecosystems and the services they provide. To address the negative impacts of disturbance, progressive rehabilitation is commonly advocated. However, there is little research focusing on how these impacts affect ecosystem services within mine sites and changes over time. The aim of this study was to assess the cumulative impacts of mining disturbance and rehabilitation on ecosystem services through mapping and quantifying changes at multiple spatial and temporal scales. Four ecosystem services including carbon sequestration, air quality regulation, soil conservation and water yield were assessed in 1989, 1997, 2005 and 2013. Disturbance and rehabilitation was mapped using LandTrendr algorithm with Landsat. We mapped spatial patterns and pixel values for each ecosystem service with corresponding model and the landscape changes were analyzed with landscape metrics. In addition, we assessed synergies and trade-offs using Spearman's correlation coefficient for different landscape classes and scales. The results showed that carbon sequestration, air quality regulation and water yield services were both positively and negatively affected by vegetation cover changes due to mined land disturbance and rehabilitation, while soil conservation service were mainly influenced by topographic changes. There were strong interactions between carbon sequestration, air quality regulation and water yield, which were steady among different spatial scales and landscape types. Soil conservation correlations were weak and changed substantially due to differences of spatial scales and landscape types. Although there are limitations associated with data accessibility, this study provides a new research method for mapping impacts of mining on ecosystem services, which offer spatially explicit information for decision-makers and environmental regulators to carry out feasible policies, balancing mining development with ecosystem services provision. © 2020 Elsevier B.V.

ANC–BNC titrations and geochemical modeling for characterizing calcareous and siliceous mining waste

- Drapeau, Clémentine, Delolme, Cécile, Vézin, Clément, Blanc, Denise, Baumgartl, Thomas

  • Authors: Drapeau, Clémentine , Delolme, Cécile , Vézin, Clément , Blanc, Denise , Baumgartl, Thomas
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Minerals Vol. 11, no. 3 (2021), p. 1-16
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  • Description: Pyrite and calcite are mineral phases that play a major role in acid and neutral mine drainage processes. However, the prediction of acid mine drainage (AMD) or contaminated neutral drainage (CND) requires knowledge of the mineral composition of mining waste and the related potential for element release. This paper studies the combination of acid–base neutralizing capacity (ANC–BNC) with geochemical modeling for the characterization of mining waste and prediction of AMD and CND. The proposed approach is validated with three synthetic mineral assemblages: (1) siliceous sand with pyrite only, representing mining waste responsible for AMD, (2) siliceous sand with calcite and pyrite, representing calcareous waste responsible for CND, and (3) siliceous sand with calcite only, simulating calcareous matrices without any pyrite. The geochemical modeling approach using PHREEQC software was used to model pH evolution and main element release as a function of the added amount of acid or base over the entire pH range: 1 < pH < 13. For calcareous matrices (sand with calcite), the results are typical of a carbonated environment, the geochemistry of which is well known. For matrices containing pyrite, the results identify different pH values favoring the dissolution of pyrite: pH = 2 in a pyrite-only environment and pH = 6 where pyrite coexists with calcite. The neutral conditions can be explained by the buffering capacity of calcite, which allows iron oxyhy-droxide precipitation. Major element release is then related to the dissolution and precipitation of the mineral assemblages. The geochemical modeling allows the prediction of element speciation in the solid and liquid phases. Our findings clearly prove the potential of combined ANC–BNC experiments along with geochemical modeling for the characterization of mining waste and the assessment of risk of AMD and CND. © 2020 by the authors. *Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Thomas Baumgartl” is provided in this record**

A small-scale test for rapid assessment of the soil development potential in post-mining soils

- Bucka, Franziska, Pihlap, Evelin, Kaiser, Jara, Baumgartl, Thomas, Kögel-Knabner, Ingrid

  • Authors: Bucka, Franziska , Pihlap, Evelin , Kaiser, Jara , Baumgartl, Thomas , Kögel-Knabner, Ingrid
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Soil and Tillage Research Vol. 211, no. (2021), p.
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  • Description: When ceasing brown coal mining activities, the restoration of the disturbed landscape is required, and a rapid development of functional soils is of utter importance for the rehabilitation of these areas. In order to accelerate soil development and rehabilitation, soils are designed or engineered by applying alternative approaches in order to construct a soil-like substrate, e.g., by mixing different substrates and organic carbon (OC) sources. We used a rapid and easy to perform laboratory approach to simulate the initial steps of soil development. We investigated the mixtures’ properties and the initial development of soil structure, in order to identify suitable soil mixtures for subsequent field trials. We tested six different mixtures composed of increasing complexity, based on the mixture used for a rehabilitation program at a coal mine in southern Australia. The components were overburden, fly ash, paper mulch, brown coal and plant litter. We performed a short-term laboratory incubation in regularly irrigated microcosms for forty days at constant water tension. Our results showed that the addition of fly ash to the overburden led to a higher moisture content. Fly ash together with paper mulch and brown coal improved nutrient supply and OC content, but led also to a very wide C/N ratio >95. The molecular composition of the paper mulch and brown coal OC shows the potential for long-term OC storage because of slow microbial degradation. Microbial activity, as measured by CO2 release, was high in all mixtures with litter addition, but only the additional presence of fly ash, brown coal and paper mulch led to a higher microbial carbon use efficiency (CUE). Soil structure formation, as measured by isolating water-stable aggregates, was induced in all mixtures and intensified in the presence of litter. In the mixtures with litter, there was a predominant formation of large macroaggregates (0.63−30 mm) which stored >80 % of the total OC. We suggest that the complex rehabilitation mixture indicates the potential for soil structure development within a short timeframe also in field scale, because the tested substrates are known to store moisture, deliver nutrients and OC for sustainable microbial growth. © 2021 Elsevier B.V.

An empirical analysis of sediment export dynamics from a constructed landform in the wet tropics

- Yavari, Shahla, McIntyre, Neil, Baumgartl, Thomas

  • Authors: Yavari, Shahla , McIntyre, Neil , Baumgartl, Thomas
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Water (Switzerland) Vol. 13, no. 8 (2021), p.
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  • Description: Although plot-scale erosion experiments are numerous, there are few studies on constructed landforms. This limits the understanding of their long-term stability, which is especially important for planning mined land rehabilitation. The objective of this study was to gain insight into the erosion processes in a 30 × 30 m trial plot on a mine waste rock dump in tropical northern Australia. The relationships between rainfall, runoff and suspended and bedload sediment export were assessed at annual, seasonal, inter-event and intra-event timescales. During a five-year study period, 231 rainfall– runoff–sediment export events were examined. The measured bedload and suspended sediments (mainly represented in nephelometric turbidity units (NTU)) showed the dominance of the wet season and heavy rainfall events. The bedload dominated the total mass, although the annual bedload diminished by approximately 75% over the five years, with greater flow energy required over time to mobilise the same bedload. The suspended load was more sustained, though it also exhibited an exhaustion process, with equal rainfall and runoff volumes and intensities, leading to lower NTU values over time. Intra-event NTU dynamics, including runoff-NTU time lags and hysteretic behaviours, were somewhat random from one event to the next, indicating the influence of the antecedent distribution of mobilisable sediments. The value of the results for supporting predictive modelling is discussed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Inspection of open-pit mine drainage characteristics with a horizontal borehole camera

- Perdigao, Cristhiana, Dyson, Ashley, Yaghoubi, Mohammadjavad, Baumgartl, Thomas

  • Authors: Perdigao, Cristhiana , Dyson, Ashley , Yaghoubi, Mohammadjavad , Baumgartl, Thomas
  • Date: 2021
  • Type: Text , Conference paper
  • Relation: 14th Baltic Sea Region Geotechnical Conference, BSGC 2020 Vol. 727
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  • Description: Horizontal bores and drains are crucial infrastructures for maintaining the stability of large open-pit mines. Induced deformations as the result of mining activities and the infiltration of water from large surface catchments during heavy rain events can cause the build-up of pore water pressures in brown coal batters. This can potentially lead to catastrophic slope failures. Horizontal boreholes and drains are commonly installed at shallow inclines and typically range in length from 150 to 400 metres. Due to complexities in surveying lengthy horizontal bores, the long-term internal properties of these structures are poorly understood. In this research, a specialised horizontal borehole camera was developed to observe a range of factors influencing borehole performance including the identification of fractured or jointed material, borehole geometry and features, and locationally dependent water outflow and drainage paths. Investigations were undertaken at an operational brown coal mine in the Latrobe Valley, located in Victoria, Australia. Features observed on the profile of horizontal bores are discussed, with an emphasis on providing in-situ material characterisation and for the purposes of maintaining stable mine batters. © Published under licence by IOP Publishing Ltd.

Lead mobilization and speciation in mining waste : experiments and modeling

- Drapeau, Clementine, Argane, Rabei, Delolme, Cecile, Blanc, Denise, Baumgartl, Thomas

  • Authors: Drapeau, Clementine , Argane, Rabei , Delolme, Cecile , Blanc, Denise , Baumgartl, Thomas
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Minerals Vol. 11, no. 6 (2021), p.
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  • Description: Mining produces significant amounts of solid mineral waste. Mine waste storage facilities are often challenging to manage and may cause environmental problems. Mining waste is often linked to contaminated mine drainage, including acidic waters with more or less elevated concentrations of trace metals such as lead. This work presents a study on the mobilization of lead from waste from two typical mining sites: Zeida and Mibladen, two now-closed former Pb–Zn mines in the Moulouya region of Morocco. Our research investigates the mobilization potential of Pb from the waste of these mines. The study involved acid–base neutralization capacity tests (ANC–BNC) combined with geochemical modeling. Experimental data allowed for the quantification of the buffering capacity of the samples and the mobilization rates of lead as a function of pH. The geochemical model was fitted to experimental results with thermodynamic considerations. The geochemical model allowed for the identification of the mineral phases involved in providing the buffering capacity of carbonated mining waste (Mibladen) and the meager buffering capacity of the silicate mining waste (Zeida). These cases are representative of contaminated neutral drainage (CND) and acid mine drainage (AMD), respectively. The results highlight the consistency between the ANC–BNC experimental data and the associated modeling in terms of geochemical behavior, validating the approach and identifying the main mechanisms involved. The modeling approach identifies the dissolution of the main solid phases, which impact the pH and the speciation of lead as a function of the pH. This innovative approach, combining ANC–BNC experiments and geochemical modeling, allowed for the accurate identification of mineral phases and surface complexation phenomena, which control the release of lead and its speciation in drainage solutions, as well as within solid phases, as a function of pH. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Thomas Baumgartl” is provided in this record**

Soil organic carbon in rehabilitated coal mine soils as an indicator for soil health

- Baumgartl, Thomas, Chan, J., Bucka, F., Pihlap, E.

  • Authors: Baumgartl, Thomas , Chan, J. , Bucka, F. , Pihlap, E.
  • Date: 2021
  • Type: Text , Conference paper
  • Relation: 14th International Conference on Mine Closure, Mine Closure 2021 Vol. 2021-August
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  • Description: Rehabilitation intends to provide a safe, stable and sustainable environment. Soil health is often used as a parameter, which describes the success of reclamation, the performance of the soil and its associated soil system functions. Reclaimed and therefore young soils are in general deprived of soil organic carbon. They are not in equilibrium with their environment and undergo changes over time, faster than natural and developed soils. Carbon content as a summarising criterion for soil health status can be used as an indicator as it reflects the performance of important soil processes, like water holding capacity, drainage and aeration potential and nutrient supply and storage. It is well established that carbon content affects soil functions like hydraulic conductivity by creating structural elements through aggregation processes. Increasing carbon content leads to increased water infiltration, reduced surface runoff and erosional risks, and increases the exchange rate of gases and improves aeration and has in general positive consequences for microbiological activity. Results from a study of soil covers of different ages emphasise this consequence. The evaluation of the rehabilitation success in coal mining using carbon content is complicated due to the difficulty distinguishing between carbon forms: Organic carbon naturally formed by decomposition vs. carbon originating from coal as coal dust or charred material. Furthermore, the assessment of the performance of rehabilitated soils is strongly affected by climatic conditions, which affect the production, decomposition and translocation of organic matter. Litter and dead organic matter from plants are decomposed on the soil surface and incorporated through organisms into the soil profile. Dissolvable organic constituents may be transported with infiltrating water down the profile. Consequently, carbon is primarily concentrated close to the surface. In semi-arid environments the accumulation depth may only be centimetres as was found from a study on the performance of the carbon pool of rehabilitated soils across sites up to 35 years of age. This has implications for the sampling strategy and the assessment of the performance of soils over time. As the carbon content in soils at coal mines can be affected by precipitation and incorporation of coal dust into the soil, the content of new organic carbon representing soil health status can be misleadingly interpreted. Therefore, separation of carbon fractions is necessary to identify the "green" carbon pool (carbon originating from plant litter and residue) as best as possible and extract the correct fraction to assess the performance of soil development. A method has been developed and is presented which allows the separation between the various carbon pools. From the presented study, the following conclusions were drawn: 1) Soil carbon is an easy to measure indicator for the assessment of the performance of soil health of rehabilitated soils; 2) soil functional properties are affected by carbon content and age and hence change with soil development; 3) only green carbon represents soil health and appropriate methodology has to be in place to exclude other carbon pools; 4) carbon storage in rehabilitated soils of semi-arid environments of Australia is below that of natural soils. © 2021, Qualified Mining Consultants LLC,.All right reserved.

Mineralogy of tailings: challenges to usual routines of characterization

- Kelm, U., Baumgartl, Thomas, Edraki, M., Gutiérrez, L., Jerez, O., Morales, J., Novoselov, A.

Characterising soil physical properties of selected temperate highland peat swamps on sandstone in the Sydney basin bioregion

- Shaygan, Mandana, Baumgartl, Thomas, McIntyre, Neil

  • Authors: Shaygan, Mandana , Baumgartl, Thomas , McIntyre, Neil
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Journal of Hydrology: Regional Studies Vol. 40, no. (2022), p.
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  • Description: Study region: Sydney Basin, New South Wales, Australia. Study focus: Some of Temperate Highland Peat Swamps on Sandstone of Sydney Basin overlie existing underground mining areas, which may impact the hydrological fluxes into and out of the swamps. Understanding and predicting these potential impacts and their consequences for swamps’ vegetation requires knowledge of the relevant physical properties of the soil, however such knowledge is almost completely absent from the literature. This study addresses this gap, and provides new insight into the degree and nature of variability between swamp sites, and between groups of swamps, the soil properties controlling these variabilities and the classification of these swamps in the context of peatland. Soil samples were collected up to a depth of 750 mm from ten sites in Upper Nepean and Newnes Plateau swamps. Samples were analysed for organic matter, bulk density, texture, saturated hydraulic conductivity and water retention characteristics. New hydrological insights: Not only the organic matter, but also bulk density and sand content control soil physical properties of the swamps. Soil properties vary between swamps; however, the variabilities were not large relative to those found in peatlands globally. These THPSS of the Sydney Basin cannot be classified as peatland and so their soil parameters cannot be estimated through the generalisation of peatland soil physical properties. It is concluded that the insights into soil properties provide new scope for developing hydrological models to assist in hydrological and ecological impacts analysis of the swamps. © 2022 The Authors

The impacts of high salinity and polymer properties on dewatering and structural characteristics of flocculated high-solids tailings

- Boshrouyeh Ghandashtani, Mohammad, Costine, Allan, Edraki, Mansour, Baumgartl, Thomas

  • Authors: Boshrouyeh Ghandashtani, Mohammad , Costine, Allan , Edraki, Mansour , Baumgartl, Thomas
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Journal of Cleaner Production Vol. 342, no. (2022), p.
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  • Description: In seeking to better understand the inline flocculation technique for enhanced water recovery from concentrated fine-particle suspensions, polymers of different molecular weight (MW) and chemistry were used to treat a synthetic tailings slurry in a low-shear mixer for continuous flocculation under controlled conditions. The effects of dissolved salts in the slurry and polymer solution make-up water on dewatering performance were evaluated for conventional acrylamide/acrylate copolymers (BASF Magnafloc® products) and an alternative functional chemistry polymer (BASF Rheomax® DR 1050). The properties of the separated liquid and solid phases were examined to understand the impacts of salinity and polymer type on the formation of rapidly dewatering flocculated material. Higher concentrations of NaCl (0.006–0.6 M) and CaCl2 (0.006–0.06 M) salts in the unflocculated slurries formed larger coagulated structures, with focussed beam reflectance measurement (FBRM) showing greater pre-aggregation for the divalent salt. NaCl slurries show edge-to-edge (EE) and edge-to-face (EF) inter-particle associations that are open and easily disrupted while more compact face-to-face (FF) contacts are observed in CaCl2 slurries. For concentrated NaCl slurries, the dosing of medium-to-high MW polymers is generally preferred to maximise net water recovery, with the implication being that bridging mechanisms are still at play in high solids applications. In calcium-enriched slurries, the lower MW conventional copolymer gave comparatively better water returns than the other polymers when applied under low shear conditions, highlighting quite distinct aggregation processes compared to low solids flocculation. These results provide insight on the fundamental complexity of the ionic strength dependence of high solids-high dosage tailings flocculation, towards informing reagent polymer dosing and offering greater flexibility for end-of-pipe dewatering schemes. © 2022

Reclamation of salt-affected land: A review

- Shaygan, Mandana, Baumgartl, Thomas

  • Authors: Shaygan, Mandana , Baumgartl, Thomas
  • Date: 2022
  • Type: Text , Journal article
  • Relation: Soil systems Vol. 6, no. 3 (2022), p. 61
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  • Description: Reclamation of salt-affected soil has been identified by the FAO as being critical to meet the needs to increase agricultural productivity. This paper reviews commonly used reclamation methods for salt-affected soils, and provides critical identifiers for an effective reclamation practice of salt-affected soil. There are widely used methods to reduce salinity and sodicity of salt-affected soils, including salt leaching, addition of amendments, revegetation using halophytes and salt scrapping. Not all reclamation techniques are suitable for salt-affected land. The reclamation strategy must be tailored to the site, and based on understanding the soil, plant and climate interactions. On some occasions, a combination of techniques may be required for reclamation. This can include salt scrapping to remove salts from the surface soil, the addition of physical amendments to improve soil pore systems and enhance salt leaching, followed by amelioration of soil by chemical amendments to preserve soil physical conditions, and then halophyte establishment to expand the desalinization zone. This study reveals that soil hydro-geochemical models are effective predictive tools to ascertain the best reclamation practice tailored to salt-affected land. However, models need to be calibrated and validated to the conditions of the land before being applied as a tool to combat soil salinity.
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